Figure 9. Global methane reservoirs, fluxes,
and turnover times. Major
reservoirs are underlined, pool sizes and fluxes are given in Tg (1012 g) CH4 and Tg CH4 yr-1. Turnover times (reservoir divided by largest flux to or from reservoir ) are in
parentheses. To convert Tg CH4 to moles C, multiply by 6.25 x 1010.
The methane budget is less than 1% of the Earth's carbon budget.
Methane is present in quantity in only three reservoirs on Earth: as natural gas associated with fossil fuel reservoirs, as hydrates or clathrates (a cage-like structure of water ice that
contains methane), and in the atmosphere, which is the smallest reservoir. Methane in the atmosphere is photochemically oxidized, and the recently observed increase in atmospheric concentrations is a result of an imbalance between sources and the major s
ink, photochemical oxidation. Research on methane, an important greenhouse gas, has focused on fluxes influencing the atmosphere.